The present invention relates generally to an improved guide tube arrangement for assisting in the handling of a cardiac pacer electrode and lead assembly during fixation of the electrode to the heart of a patient, and more specifically to such a guide tube means which employs a coaxially arranged rod which releasably retains the electrode and its insulative pad and which is arranged to dislodge the electrode lead from the sleeve or tube upon withdrawal of the rod from the sleeve.
A significant feature of the guide tube means of the present invention is the formation of a slack segment or loop adjacent the site of the fixed electrode substantially immediately upon release of the electrode and its insulative pad from the guide tube assembly.
Devices for assisting in the fixation or securing of electrodes into body tissue have been known in the past and utilized. Certain of these devices are disclosed in U.S. Pat. No. 3,875,947. In these devices, however, the arrangement is such that the electrode remains secured to the guide tube means until full release of the lead has been achieved. Also, no slack segment or loop is provided until the electrode and lead assembly are substantially fully released from the guide device.
Electrodes having a helical shape are in common usage at this time. Such devices are disclosed in U.S. Pat. No. 4,011,861, among others. Such electrodes have the advantage of being sutureless upon fixation. Furthermore, fixation is reasonably stable, and dislodgement has not been an ordinary or frequent complication. In order to avoid entanglement or application of torque to the lead member, particularly in the area adjacent the point where the insulative pad joins the cylindrical lead, means such as a slotted tube have been proposed for avoiding the generation of such forces.
As will be appreciated, a helical electrode will ordinarily be provided in an assembly which includes the electrode structure per se, the conductive leads which are arranged to couple the electrode to the pulse generator, and an insulative backing or pad member which isolates and insulates the junction point between the conductors of the leads and the electrode. The insulative backing or pad further provides a means for delivering torque to the helical electrode for fixation.
The electrode leads are normally insulated with silicone rubber, with such material being inert to body fluids, and further providing a high degree of flexibility for the assemblies. Examples of such conductive leads are found in U.S. Pat. No. 4,033,355, among others. Because of the flexibility of the leads, precautions should be taken in order to avoid having the leads becoming entangled during the implant operation, and specifically during fixation. Apparatus of the type including a slotted guide tube has been helpful in confining the leads during the fixation operation.